Medicament pumps, such as, the peristaltic pump disclosed in commonly assigned U.S. Pat. No. 4,576,556, which is incorporated herein by reference, are well known in the prior art and have wide application in the medical field. A typical application for such a pump is implanting the pump within a patient's body for treating a neurodegenerative disease or trauma, as is disclosed in commonly assigned U.S. Pat. No. 5,711,316, which is incorporated herein by reference. Other applications are also well known. The term "medicament pump" as used herein, refers to any device for delivering medicaments including, but not limited to, bladder pumps, accumulator pumps, fixed-rate bellows pumps, and the like.
Implantable devices, such as medicament pumps, are in frequent use for delivering drugs or other liquid medications over long periods of time to selected locations in the human body. These devices commonly include a drug reservoir, catheter means connected to the reservoir to transport the drug and a pumping mechanism to propel the drug in some metered or constant flow dosage to the desired location. Over time, the drug in the reservoir becomes depleted and it is necessary to refill the device with a new supply of drug. In order to avoid the need for surgery in order to access and refill the device, it is desirable to have the ability to refill the drug reservoir percutaneously. This is commonly done by providing the medicament pump with a resilient resealable reservoir fill port septum which is accessible by injecting a hypodermic needle through the skin and into the septum thereby providing access to refill the reservoir.
In such devices a catheter access port septum is often provided in addition to the reservoir fill port septum. The catheter access port septum is also accessible percutaneously by hypodermic needle. This septum provides direct access to the catheter bypassing the pump and allows a bolus of drug or fluid medication to be administered directly into the body at the site of the catheter.
Although providing a catheter access port septum is both desirable and advantageous a problem can develop if the person refilling the reservoir incorrectly injects the drug into the catheter access port septum instead of the reservoir fill port septum. This results in the drug being administered directly to the body. This may potentially cause an overdose of drug or other serious problems because the pump should administer the drug over a period of time.
This problem has been addressed previously. For instance, U.S. Pat. No. 5,328,465, issued to Kratoska et al. on Jul. 12, 1994, which is incorporated herein by reference, discloses a screen for covering a medicament pump catheter access port. The screen limits access to the catheter access port septum to hypodermic needles smaller than a predetermined size. A few shortcomings of such screens are that they tend to damage hypodermic needles when a needle is inserted not aligned with a hole in the screen. Such screens are also relatively expensive and difficult to manufacture.
U.S. Pat. No. 4,573,994 issued to the Fischell et al. on Mar. 4, 1986, discloses a conical depression as part of a system and method for accessing a medicament pump reservoir access port. Fischell et al., however, does not disclose limiting access to a port by hypodermic needles smaller than a predetermined size.
Accordingly, a need exists for a simplified, less expensive device and method that eliminates, or at least reduces the possibility of, inadvertent injections of drug directly into the catheter access port without damaging hypodermic needles.